5 replies to this topic

[muthukmaar]

We have a 290 tph boiler at 105 kg/cm² pressure.  Why couldn't we produce steam at any pressure lower if we could modify the Boiler Feed water System?

[PingPong]

Problem definition is really too vague.

 

In general: lower pressure means bigger steam volumetric flow, which would be a problem for the steam drum (separating water from steam) and for the piping handling steam/water mixture.

 

Best check with boiler vendor.

[Rahimzadeh]

Dear:

In industry with letdown station it become possible

[shan]

Besides lowering BFW pressure, you should check the approaching temperature and if there is steaming in the boiler economizer section.  Also, you need check the heat balance in the boiler vaporizer section and superheater section.  

[Bobby Strain]

And, why do you want to produce lower pressure steam? It makes no sense to me. You probably have turbines that use the steam to power compressors and/or generators. Lower pressure would be less efficient in such case.

 

Bobby

[K RAVI VARMA]

Higher the energy higher is the Availability of thermal energy for conversion into mechanical energy.
 

Workdone W = ò P dv

 

where W denotes the work done by the system during the whole of the reversible process, P the pressure,  dV the difference volume. Higher the pressure higher is the work done for a definite change in volume of the fluid.

 
Corollaries of II Law of Thermodynamics, the Carnot Principle states "The efficiency of heat engine does not depend on the fluid employed, but depends only upon the temperature levels between which it works"
 
Interpreting, the efficiency of heat engine depends only upon difference in High temperature of the source and Low Temperature of the sink. Higher the difference, higher is the efficiency
 
Hence to achieve higher efficiency in steam engines as well as to limit pressure losses during transmission and distribution, Steam is generated at highest temperature and consumed at the lowest temperature possible, as system permits.
 
Feasibility of modifying BFW pressure is very limited. Lowering Boiler feed water pressure, causes steam generation in Economiser itself, resultant two phase flow causes line hammering which is unsafe,  the increased volume of two phase flow generated, results in higher pressure drop, limiting Boiler feed water flow to Boiler and eventually limiting load of the boiler. It is not BFW pressure that decides to bring sustainable change, but the design temperature and pressure of steam engines at work within the factory that decides the pressure to the working model

 

regards

K Ravi Varma

Edited by K RAVI VARMA, 25 December 2018 - 09:07 PM.